Treatment of exposed silver halide emulsion with acidic hardening bath following by alkaline activating bath

ABSTRACT

EXPOSED PHOTOGRAPHIC LAYERS PARTICULARLY LAYERS WHICH CONTAIN COLOR COUPLERS, ARE HARDENED GEFORE PROCESSING BY TREATING THE EXPOSED LAYER WITH PREHAREDENING BATHS, HAVE A PH-VALUE IN THE SIDE RANGE AND WHICH CONTAIN HARDENING AGENTS.

United States Patent No Drawing. Filed Aug. Claims priority, application Germany, Aug. 21, 1969, P 19 42 562.8 Int. Cl. G03c 1/30 US. Cl. 96-111 4 Claims ABSTRACT OF THE DISCLOSURE Exposed photographic layers particularly layers which contain color couplers, are hardened before processing by treating the exposed layer with prehardening baths, have a pH-value in the side range and which contain hardening agents.

The invention relates to a process for hardening exposed photographic layers, particularly those photographic layers which contain color couplers, by treating the exposed layers with prehardening baths.

It is known to develop photographic silver halide emulsions at elevated temperatures so as to reduce the processing time. At elevated bath temperatures, however, emulsions which consist at least partly of gelatin and which have been hardened in the conventional manner become soft. In addition, in multilayered films, the layers tend to become detached and severe wrinkling occurs. Both effects are particularly marked if the layers contain watersoluble diffusion resistant color couplers. 1f the layers are hardened to a greater degree, the sensitivity is lost and the 'y-value of the emulsions changes.

Attempts have been made to prevent melting and detachment of the layers and mechanical damage to the layers during processing by using before development hardening baths which contain inorganic hardeners such as aluminium sulfate or potassium aluminium alum or organic hardeners, e.g. aldehydes such as formaldehyde, glyoxal, succinaldehyde and glutaraldehyde. This leads to considerable difiiculties, however, because the hardeners are easily carried into the developer. A bath must therefore be interposed between the hardening bath and developer bath to eliminate the aldehydes. Moreover, when water-soluble diffusion resistant color couplers are used, preliminary baths which contain compounds with aldehyde groups cannot be used because the color components are changed irreversible by such a treatment.

Although hardening of exposed photographic layers with such prehardening baths is advantageous in itself, the prehardening baths mentioned above have not given satisfactory results in practice owing to the disadvantages mentioned above.

It is among the objects of the present invention to provide new prehardening baths or combinations of various storage and which do not adversely influence the subsequent development process.

A process for hardening photographic layers has now "ice been found in which an exposed photographic material which comprises at least one silver halide gelatin emulsion layer which may contain color coupler is treated with a prehardening bath before development, the exposed material being first treated with an aqueous bath at a pH of between 3 and 7 and which contains 0.5 to 10% by weight of a dissolved hardener which at these pH values has little or no hardening effect on gelatin, and additives which inhibit swelling, followed by a second aqueous bath having a pH of between 11 and 14 which also contains additives which inhibit swelling.

The advantage of the process of the invention is that the step in which diffusion of hardener into the layer occurs is separate from the actual hardening process. Little or no hardening of the photographic layer should take place in the first bath, which contains the hardener. Suitable hardeners for this bath are, therefore, those which have a very low hardening effect at acid pH values of between 3 and 7. In the second, alkaline bath which has a pH value of above 11, the hardener adsorbed in the layer then reacts with the gelatin of the photographic layer.

Hardening should then proceed as rapidly as possible in this bath.

Suitable hardeners are therefore quite generally those which have no effect in acid pH ranges but a very rapid hardening effect at alkaline pH values. Especially suitable are those compounds which contain at least two groups which are active as hardeners, such as active double bonds or groups which can be converted into active double bonds at alkaline pH values. The first class hardeners include eg the following:

(1) Methylene bisacrylamide (2) 1,3,5-N,N,N"-tris-acryloyl hexahydrotriazine (3 1,3-bis-vinylsulfonyl-4,6-dimethylbenzene (4) Resorcinol divinyl sulfonic acid esters (5) 2,4,6-trisacryloxy-triazine-1,3,5

(6) 1,3,5-tris-vinylsulfony1hexahydrotriazine-1,3,5

The second class of compounds includes quaternary ammonium salts which can be obtained by reacting the above mentioned compounds with tertiary ammonium salts, e.g. those described in Belgian Pat. No. 740,599 or in British Pat. No. 1,158,263, such as the following:

( 10) Reaction product of compound 2 with diazabicyclooctane hydrochloride (11) Reaction product of compound 2 with pyridinium chloride 4 which is almost unavoidable in automatic processes, the development process is not adversely influenced. The

(12) Reaction product of compound 6 with diazabicyclooctane hydrochloride (13) Reaction product of compound 2 with N-methylmorpholinium chloride In particular suitable are compounds Which contain at least 2 vinylsulfone or acryloyl groups, especially those of the triazine or hydrotriazine series.

The amount of the hardening agent in the acid or neutral bath can be varied Within wide limits. Preferred are concentrations of between 100 and g./l. of the bath.

Additives which inhibit swelling are added to both the prehardening baths in order to suppress swelling of the exposed photographic layers in these baths. Suitable additives for this purpose are in particular neutral salts of alkali metals with strong acids such as sodium sulfate, potassium sulfate, lithium sulfate or sodium phosphate.

The additives which inhibit swelling are added in such quantities that layers which have been only slightly hardened will not swell by more than about 200%. In general amounts of between 50 and 160 g./l. have proved sulficient.

The pH of the bath which contains the hardener is adjusted to a value between 3 and 7 with mineral acids and suitable buffer solutions. Inorganic acids such as hydrochloric acid or sulfuric acid, sodium acetate or sodium citrate, etc. are suitable for this purpose.

The baths may, of course, also contain other additives according to the requirements of the particular photographic process, e.g. substances which prevent fogging, such as heterocyclic compounds, e.g. benzotriazole or mercapto substituted heterocyclic compounds, or inorganic salts which have this effect, such as sodium bromide.

The second preliminary bath used, hereinafter briefiy termed the alkaline bath, consists of an aqueous solution of an additive which prevents swelling, this solution having a pH of between 11 and 14. The pH is most simply adjusted by the addition of alkali metal hydroxides. Suitable additives for preventing swelling are those mentioned earlier for bath I.

Buffers and antifog agents may also be added to the alkaline bath as described above.

The process according to the invention is superior to the known process described earlier particularly in its simplicity. The stability of the baths is particularly good. Since the first preliminary bath has only a low pH value, the stability of the usual hardeners is extremely high. The hardening reaction itself proceeds very rapidly in the alkaline bath so that only short treatment times are required. The baths used in the process of the invention are inert to the subsequent processing baths, particularly to the development bath. Even if substantial quantities of the alkaline bath are carried over into the developer bath,

10 rapid hardening in the alkaline bath results in layers which have an extremely low swelling and a high mechanical strength even when wet. Even when starting with photographic layers which have not been hardened or hardened only to a very slight extent, subsequent processing may be carried out at relatively high temperatures of up to about 50 C. after the process according to the invention has been carried out.

The photographic properties of the layers are in no way influenced by the process according to the invention.

The process according to the invention is particularly advantageous for processing color photographic materials. The photographic properties of the multi-layered materials used for this purpose also remain unchanged. Layers which have exceptionally good mechanical properties are obtained.

The processing time may vary within wide limits. A treatment time of about /2 to 1 minute is generally sufficient in the first preliminary bath which contains the hardener. The treatment time in the alkaline bath is about /2 to 3 minutes. The temperature of the baths is about 18 to 30 C., preferably about 20 C. Subsequent photographic processing need not be altered in any way and can be carried out with the baths of the usual composition.

EXAMPLE 1 A multilayered color photographic material on a cellulose triacetate layer support, comprising a red-sensitive silver halide emulsion layer which contains a cyan coupler, a green-sensitive silver halide emulsion layer which has a magenta coupler and a blue-sensitive silver halide emulsion layer which has a yellow coupler is exposed in a conventional sensitometer and after exposure it is treated with the following baths:

Preliminary bath I 800 cc. of water 5.4 cc. of sulfuric acid 154 g. of sodium sulfate 2 g. of sodium bromide 20 g. of sodium acetate 10 g. of hardener 10 made up to 1 liter pH 4.8, reaction time 60 seconds, temperature 20 C.

Preliminary bath II 800 cc. of water 4 g. of sodium hydroxide 154 g. of sodium sulfate made up to 1 liter pH 12.9, reaction time 60 seconds, temperature 20 C.

After passing through the two baths, it is processed at 40 C. as follows:

(1) Development: 3 min. (2) Short stop bath: 2 min. (3) Bleaching bath: 3 min. (4) Fixing bath: 1 min. (5) Washing: l min.

The film samples show no detachment of the layers or reticulation after processing. The melting points of the layers are above 100 C. (melting point of initial sample 56 C.). In film samples which were not passed through the two preliminary baths before processing, partial detachment of the layers had already occurred in the developer. The samples could not be processed in baths at 40 C.

- EXAMPLE 2 To demonstrate the action of the individual baths, unhardened gelatin-containing silver chlorobromide gelatin emulsion layers on a cellulose acetate layer support were subjected to processes A and B before development.

Process A 3 min. preliminary bath I 10 min. washing Process B 3 min. preliminary bath 1 5 min. preliminary bath II (composition as in Example 1) min. washing.

The solutions used as preliminary bath have the following composition:

800 cc. of water 154 g. of sodium sulfate 2 g. of sodium bromide 20 g. of sodium acetate 10 g. of hardening compound according to the following table made up to 1 l. with water, pH 4.8.

The following table shows the melting points of the layers determined after the treatment:

Melting point of layer C.)

Hardener Process A Process B The table shows that no hardening occurs in preliminary bath I with the compounds used. The bath only serves to introduce the hardener into the layer. Hardening takes place in the alkaline preliminary bath II.

The same results are obtained when the photographic emulsion is coated on a baryta paper support.

EXAMPLE 3 Prehardening of a three-layered color-photographic paper. A color photographic material of the following structure:

is exposed in a conventional sensitometer and treated with the following baths after exposure:

'Preliminary bath *I.Compositi0n 2000 ml. of water 16.2 ml. of 47% sulfuric acid 462 g. of sodium sulfate 6 g. of sodium bromide 60 g. of sodium acetate 600 ml. of a 50% solution of compound 9 made up to 3 liters pH 4.8, reaction time: 70 seconds, temperature: 20 C.

Preliminary bath Il.-Composition 800 ml. of water 4 g. of sodium hydroxide 154 g. of sodium sulfate made up to 1 liter pH 12.9, reaction time 70 seconds, temperature 20 C. This is followed by the following processing at 40 C.:

(1) Development: 70 sec.

(2) Short stop and fixing bath: 70 sec. (3) Bleach fixing bath: 70 sec.

(4) Washing: 70 sec.

The samples obtained show firm bonding of the layers, melting points above C. and no reticulation. In the samples which were not passed through preliminary baths I and II, detachment of the layers, wrinkling and partial solution of the layers already occurred in the developer bath at 40 C. Without the preliminary baths, the samples could not be processed at 40 C.

Equally good results are obtained when instead of using 600 ml. of the 50% solution of compound 9, only ml. or 60 ml. of this solution are used, in other Words the concentration in the preliminary bath is reduced from 10% to 3% and then 1%.

We claim:

1. In a process for hardening photographic layers by treating an exposed photographic material comprising at least one silver halide gelatin emulsion layer with a preliminary hardening bath followed by development, the improvement consisting of exposing the photographic material containing the silver halide gelatin emulsion layer, treating the exposed material with an aqueous bath which has a pH of between 3 and 7 containing additives which inhibit swelling and containing in hardening concentration of 0.5 to 10% by weight a non-polymeric diifusible organic compound having a relatively lesser hardening effect on the gelatin emulsion layer in a solution at a pH of between 3 and 7 than at a pH between 11 and 14 and immediately follow by subsequently treating the exposed material with a second aqueous bath which has a pH of between 11 and 14 and which also contains additives which inhibit swelling.

2. The process of claim 1, wherein the organic compound is trisacryloylor trisvinylsulfonyl triazine a reaction product thereof with an onium salt of open chain or a cyclic tertiary amine.

3. The process of claim 1, wherein the baths contain, as additives which inhibit swelling, neutral salts of alkali metals with strong inorganic acids in such quantities that the swelling of only slightly hardened layers is not more than 2.00%.

4. The process of claim 1, wherein at least one of the baths contains sodium acetate or sodium citrate.

References Cited UNITED STATES PATENTS 3,226,234 12/ 1965 Himmelmann, et al. 96-111 2,154,895 4/1939 Fricke, et al. 96-111 3,255,000 6/1966 Gates, et al. 96-111 2,994,611 8/tl96l Heyna, et al 96111 3,490,911 1/1970 Burness, et al 96--1l1 FOREIGN PATENTS 860,326 2/ 1961 Great Britain 96--111 NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, JR., Assistant Examiner US. Cl. X.R. 96-48; 260-117 4 

